全文获取类型
收费全文 | 547篇 |
免费 | 87篇 |
国内免费 | 42篇 |
专业分类
化学 | 289篇 |
晶体学 | 4篇 |
综合类 | 13篇 |
数学 | 8篇 |
物理学 | 362篇 |
出版年
2022年 | 7篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 16篇 |
2009年 | 24篇 |
2008年 | 19篇 |
2007年 | 26篇 |
2006年 | 29篇 |
2005年 | 19篇 |
2004年 | 67篇 |
2003年 | 38篇 |
2002年 | 79篇 |
2001年 | 50篇 |
2000年 | 60篇 |
1999年 | 29篇 |
1998年 | 49篇 |
1997年 | 25篇 |
1996年 | 10篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有676条查询结果,搜索用时 0 毫秒
671.
672.
We investigate the formation and distribution of the solid electrolyte interface (SEI) layer on a graphite anode with two additives [vinylethylene carbonate (VEC) and vinylene carbonate (VC)] in a formation process using XPS, field emission AES, and extreme high‐resolution SEM (XHR‐SEM) techniques, and we studied what factors play an important role in determining the formation of the SEI layer. The VEC‐derived SEI behaviors (morphology, thickness, compound, and balance over electrode position) on a graphite anode largely depend on the elevated temperature. The VC‐derived SEI layer is mostly formed in the initial charging step, showing simple growth (formation) behavior. It is suggested that the properties of the additives are important for SEI bonding configurations at the nanoscale film surface, and to achieve the stable SEI layer, there appears to be an effective formation process for the additive properties. This research highlights the challenges of developing a stable SEI layer with additives in the formation process for electric vehicle batteries and would make a contribution to the understanding of how formation conditions affect an SEI layer with respect to additive properties. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
673.
《Analytical letters》2012,45(14):3025-3035
ABSTRACT The paper represents a continued study of selected heavy metals concentration in the Arge? River, the fifth river in length from Romania. For the determination of metal ion concentration in Arge? river was used Atomic Absorption Spectrometry for sodium, potassium and magnesium; Direct Coupled Plasma Atomic Emission Spectrometry for calcium; Inductively Coupled Plasma Atomic Emission Spectrometry for copper, cadmium, zinc, aluminium, lead, titanium, zirconium, chromium, molybdenum, manganese, iron and nickel. Copper, cadmium, zinc and lead concentration were determined by ICP–AES and ASV and results were reliable. By comparison of the results a good agreement between these two techniques is observed. 相似文献
674.
为了解福州市冬季市售蔬菜和水果中矿物质元素含量,给福州市居民合理选择食物提供指南,用湿法消化法对样品进行预处理,经ICP—AES和ICP—MS法测定样品矿物质元素含量,采用相关分析等统计方法对结果进行了综合评价。结果表明,所测蔬菜中莲藕、小白菜、西兰花、马铃薯、四季豆、芥菜和大蒜各种矿物质含量较高,水果中青橄榄、荸荠、芦柑、草莓各种矿物质含量较高,市民可根据个人对营养的需求,合理选择,科学搭配;相关分析表明,大部分元素之间都有显著的正相关性,仅P与所测元素之间表现出一定的负相关性。可见所测蔬菜和水果中含有丰富的矿物质元素,这些矿物元素之间的交互关系主要以协同作用为主。 相似文献
675.
Lanthanide(III) (Dy, Gd, Tb and Y) ion imprinted polymer (IIP) materials were synthesized via single pot reaction by mixing lanthanide imprint ion with 5,7-dichloroquinoline-8-ol, 4-vinylpyridine, styrene, divinylbenzene and 2,2'-azobisisobutyronitrile in 2-methoxyethanol porogen. The imprint ion was removed by stirring the above materials (after powdering) with 6 mol/L HCl to obtain the respective lanthanide IIP particles. Y-Dy, Y-Gd and Dy-Gd polymer particles were obtained by physically mixing equal amounts of the respective leached individual lanthanide(III) particles. Control polymer (CP) particles were similarly prepared without imprint ion. Application of the above synthesized polymer particles was tested for separation of Y from Dy, Gd and Tb employing batch and column SPE methods using inductively coupled plasma atomic emission spectrometry for the determination. Optimization studies show that Y present in 500 mL can be preconcentrated using Dy-Gd IIP particles and eluted with 20 mL of 1.0 mol/L of HCl, providing an enrichment factor of approximately 25. Dy-Gd IIP particles offer higher selectivity coefficients for Y over other lanthanides compared to other IIP particles and commercial liquid-liquid extractants. Selectivity studies for Y over other coexisting inorganic species (other than lanthanides) were also conducted and the results obtained show a quantitative separation of Y from other inorganics other than Cu(II) and Fe(III). Furthermore, both batch and column studies indicate the purification of yttrium concentrate from 55.0 +/- 0.2 to 65.2 +/- 0.2% in a single stage of operation. 相似文献
676.
B. Karunagaran R.T. Rajendra Kumar D. Mangalaraj Sa. K. Narayandass G. Mohan Rao 《Crystal Research and Technology》2002,37(12):1285-1292
Titanium dioxide films have been deposited using DC magnetron sputtering technique. Films were deposited onto RCA cleaned p‐silicon substrates at the ambient temperature at an oxygen partial pressure of 7 × 10–5 mbar and sputtering pressure of 1 × 10 –3 mbar. The deposited films were annealed in the temperature range 673–873 K. The structure and composition of the films were confirmed using X‐ray diffraction and Auger electron spectroscopy. The structure of the films deposited at the ambient was found to be amorphous and the films annealed at 673 K and above were crystalline with anatase structure. The lattice constants, grain size, microstrain and the dislocation density of the film are calculated and correlated with annealing temperature. 相似文献